Additive manufacturing, sometimes called 3D printing, is a relatively new technology that is the process of joining materials to make parts from 3D (three-dimensional) model data, usually layer upon layer. Traditional, subtractive manufacturing techniques create shaped objects by removing material from a larger template. Traditional additive techniques, such as welding, molding, bonding and fastening, are not classified as additive manufacturing because those techniques are not driven by a 3D model nor built essentially layer by layer. Additive manufacturing typically uses a bulk stock material, such as a liquid, granular, or solid material, that is selectively formed into a layer according to an electronic input. Layers are built, typically one on top of the last, until the entire part is formed.
Additive manufacturing allows complex parts to be built without tooling and/or fixtures, and is typically employed for rapid prototyping and non-critical, complex parts. Additive manufacturing may be employed in various industries including consumer products, transportation, aerospace, robotics, medical, military, and academic research.
Additive manufacturing is typically more material efficient than traditional manufacturing. In traditional manufacturing using casting and machining, a large fraction of the stock material is scrapped. In additive manufacturing, the stock material is selectively used to form a layer. The remaining stock material remains essentially unaffected and available for future use. Further, because of the free form nature of additive manufacturing, complex structures may be formed for little to no additional cost, thus enabling low-cost, high strength-to-weight ratio parts desired for aerospace applications. However, present additive manufacturing techniques have limited applicability to supply critical structural components such as aerospace components because the parts built are not typically easy to inspect, especially very complex parts or parts with enclosed surfaces.